1. Technical Field of the Invention
The present invention relates to novel cosmetic/pharmaceutical compositions for promoting pigmentation of the skin and/or the exoskeleton thereof, comprising at least one retinoid bearing a phenol or naphthol functional group.
This invention also relates to a cosmetic regime or regimen for pigmenting the skin and/or exoskeleton thereof, comprising administering to an individual in need of such treatment at least one retinoid bearing a phenol or naphthol function.
2. Description of the Prior Art
The coloration of human skin and exoskeleton thereof (head hair, nails, other hair, etc.) depends on various factors and especially on the seasons of the year, race, sex and age. It is determined, principally, by the concentration of melanin produced by the melanocytes. The melanocytes are specialized cells which synthesize melanin by means of specific organelles, the melanosomes.
It is known to this art that in most populations brown skin color or the maintenance of a constant head of hair color are important aspirations.
Moreover, pigmentation diseases exist such as, for example, vitiligo which is an auto-immune disease characterized by the appearance of white patches on the skin, associated with a pigmentation defect.
Serious need thus exists for a product which facilitates and/or improves the pigmentation of the skin and/or its exoskeleton, more particularly the hair and the nails.
To date, various solutions have been proposed to the art of artificial coloration, by supplying exogenous dyes that are intended to color the skin and/or the hair to an extent as close as possible to its natural color, or in the field of natural coloration via stimulation of the natural pigmentation pathways.
Excellent results are, admittedly, obtained via the solutions heretofore proposed, but it nevertheless remains that the stimulation of pigmentation of the skin or exoskeleton thereof via the natural route (melanogenesis) remains the ideal pigmentation route.
In this regard, administration of compositions containing a phosphodiesterase inhibitor, prostaglandins, DNA fragments, tyrosine derivatives or, alternatively, plant extracts have been proposed; see WO-A-95/17161, WO-95/11003, WO-A-95/01773, WO-A-94/04674, WO-A-94/04122, EP-A-585,018, WO-A-93/10804, WO-A-92/20322 and WO-A-91/07945. Often, the proposed compounds are complex mixtures which exhibit no specificity.
Hence, identification of active species eliciting a beneficial effect on the pigmentation of the skin or exoskeleton remains a principal desideratum in this art.